The history of botanical pesticides reveals that their study did mainly focus on the determination of acute median lethal dose or concentration. In the current situation, it is the dire need to understand the sublethal eVects of the botanical extracts along with the traditional studies of lethal concentrations in order to comprehensively investigate the future role of the botanical extracts as pesticides. This study reveals the eVects of traditionally used medicinal plant extracts harmaline (H) and ricinine (R) either individually or in combination with Bacillus thuringiensis (Bt) on the acute toxicity and sublethal eVects on the nutrition and enzyme system of Spodoptera exigua. Harmaline and ricinine caused reduction in the growth of neonate larvae up to 93.12 and 84.31%. The EC 50 values of harmaline against fourth and Wfth instars were 0.24 and 0.27 mg/ml, but these values remained 0.49 and 0.54 mg/ml against fourth and Wfth instars after being treated with ricinine. The combination of harmaline and ricinine with Bt resulted in the increased eYciency of these chemicals as the mortality percentages signiWcantly increased up to 96 and 87.82% in signiWcantly less exposure time in case of H + Bt and R + Bt respectively, as compared to individual treatments. The nutritional analysis revealed the increased toxicity of harmaline and ricinine in combination with Bt, but H + Bt2 showed the higher eYciency with minimal relative consumption rate 2.50 mg/mg/day, relative growth rate 1.16 mg/mg/day and eYciency of conversion of ingested food 29.66% of control, respectively. Changes in antioxidant enzymes such as superoxide dismutase (SOD) and catalases (CAT) were noticed to some extent over diVerent exposure times at all the treatments. The highest SOD (+37.29%) and CAT (+29.27%) activity was observed at the 6th day of treatment with H + R + Bt2. The study clearly shows the signiWcantly increased eYciency of harmaline and ricinine in combination with Bt against S. exigua. This phenomenon can be helpful in order to develop better control strategies against diVerent notorious pests.

This study reveals the individual and synergistic effects of destruxin B (DB) (mycotoxin from Metarhizium anisoplae), tea saponin (Ts) and Bacillus thuringiensis (Bt) against Spodoptera exigua. DB, Ts and Bt reduced the growth of neonate larvae by up to 91.30, 89.17 and 77.17%. EC 50 values of DB against 4th and 5th instars were 0.17 and 0.22 mg ml Ϫ1, 0.35 and 0.41 mg ml Ϫ1 against 4th and 5th instars for Ts and 0.0031 and 0.0035 mg ml Ϫ1 after being treated with Bt. The synergism of DB and Ts with Bt resulted in the increased efficiency of these chemicals as mortality percentages significantly increased up to 94.2% with DBϩTsϩBt followed by DBϩBt with 91.99% and were significantly higher than individual treatments of Bt 65.81% and Ts 76.66%. Nutritional analysis revealed the increased toxicity of DB and Ts in combination with Bt, but DBϩBt showed higher efficiency with minimal relative consumption rate (RCR) 2.69 mg/mg/day, relative growth rate (RGR) 1.33 mg/mg/day and efficiency of conversion of ingested food (ECI) 35.77%, respectively. Changes in antioxidant enzymes, superoxidase dismutase (SOD) and catalases (CAT), were noticed to some extent over different exposure times in all treatments. The highest SOD activity was observed in individual DB treatment, while individual Bt treatment caused the highest variation in CAT values. In all treatments, SOD and CAT values fell sharply on the final day except for individual Bt treatment, with which the values were relatively stable on the final day.